[openstack-dev] [nova] Change from Mitaka: Expected UNIX signal to generate Guru Meditation (error) Reports

Matt Riedemann mriedem at linux.vnet.ibm.com
Fri Oct 30 15:02:54 UTC 2015



On 10/29/2015 4:46 PM, Davanum Srinivas wrote:
> Matt,
>
> Yes, Sean already opened a critical bug -
> https://bugs.launchpad.net/oslo.reports/+bug/1510740
>
> Please note that this change was added to oslo.reports *after* the
> liberty release in support of Mitaka. So i am not sure why we need to
> add it to liberty release notes. Also this is a consequence of NOT
> having version caps which was a decision a while ago as well.
>
> -- DIms
>
> On Fri, Oct 30, 2015 at 4:47 AM, Matt Riedemann
> <mriedem at linux.vnet.ibm.com <mailto:mriedem at linux.vnet.ibm.com>> wrote:
>
>
>
>     On 10/21/2015 7:43 AM, Kashyap Chamarthy wrote:
>
>         Background
>         ----------
>
>         Oslo Guru Meditation (error) Reports (GMR)[*] are a useful debugging
>         mechanism that allows one to capture the current state of a Nova
>         process/executable (e.g. `nova-compute`, `nova-api`, etc).
>
>         The way to generate the error report is to supply the 'User-defined
>         signal', SIGUSR1, when killing a Nova process.  E.g.
>
>               $ kill -USR1 `pgrep nova-compute`
>
>         which results in GMR being printed to your standard error ('stderr')
>         stream, wherever it ends up being redirected to (e.g. to a
>         corresponding
>         Nova process-specific log file, otherwise, on systemd-enabled
>         systems,
>         to its journal).
>
>
>         Change in Mitaka (and above)
>         ----------------------------
>
>           From the upcoming Mitaka release onwards, the default expected
>         UNIX
>         signal to generate GMR has been changed[1] from USR1 to USR2
>         (another
>         User-defined singal), because the USR1 is reserved by Apache
>         'mod_wsgi'
>         for its own purpose.
>
>         So, to generate GMR, from Mitaka release:
>
>               $ kill -USR2 `pgrep nova-compute`
>
>         A corresponding Nova documentation change[2] has been submitted to
>         reflect this new reality.
>
>
>         [1] https://review.openstack.org/#/c/223133/ --
>         guru_meditation_report:
>               Use SIGUSR2 instead of SIGUSR1
>         [2] https://review.openstack.org/#/c/227779/ -- doc: gmr: Update
>               instructions to generate GMR error reports
>
>
>         [*] References
>         --------------
>
>         Related reading:
>
>         - http://docs.openstack.org/developer/nova/gmr.html
>         - http://docs.openstack.org/developer/oslo.reports/usage.html
>         - https://wiki.openstack.org/wiki/GuruMeditationReport
>         -
>         https://www.berrange.com/posts/2015/02/19/nova-and-its-use-of-olso-incubator-guru-meditation-reports/
>
>
>     Looks like this broke some tooling in the gate job runs where gmr's
>     are created at the end of the service logs when the services exit.
>     Here is a mitaka change with grenade on the liberty side with the
>     gmr at the end:
>
>     http://logs.openstack.org/97/227897/13/check/gate-grenade-dsvm/27723a9/logs/old/screen-n-cpu.txt.gz
>
>     And on the new side it's gone:
>
>     http://logs.openstack.org/97/227897/13/check/gate-grenade-dsvm/27723a9/logs/new/screen-n-cpu.txt.gz
>
>     So obviously an upgrade impact, I'm hoping we get this into the
>     liberty release notes as something to change when people move up to
>     oslo.reports 1.6.0.
>
>     We should also get the gate tooling fixed around this, I'm not sure
>     where that was configured/triggered though, sdague probably knows.
>
>     --
>
>     Thanks,
>
>     Matt Riedemann
>
>
>
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>
>
> --
> Davanum Srinivas :: https://twitter.com/dims
>
>
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I guess upper-constraints in stable/liberty is 0.5.0 for oslo.reports 
[1] so people shouldn't be using anything newer than than with liberty 
deployments. So nothing needed in the release notes there I suppose.

But I agree we should probably have a deprecation cycle on this.

[1] 
https://github.com/openstack/requirements/blob/stable/liberty/upper-constraints.txt#L197

-- 

Thanks,

Matt Riedemann




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